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Special Issue "Micro Flow Controllers"

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A special issue of Micromachines (ISSN 2072-666X).

Deadline for manuscript submissions: closed (30 January 2012)

Special Issue Editor

Guest Editor
Prof. Dr. Joost Lötters (Website)

1 Transducers Science and Technology (TST), MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
2 Bronkhorst High-Tech BV, Nijverheidsstraat 1A, 7261 AK Ruurlo, The Netherlands
Interests: Design, modelling, fabrication and application of microfluidic handling systems, including MEMS thermal and Coriolis flow sensors and controllers, MEMS pressure sensors, MEMS control valves and micromachined flow analysis sytems such as multiparameter flow measurement systems and micro Wobbe index meters

Special Issue Information

Dear Colleagues,

Worldwide, accurate measurement and control of small and extremely small mass flow rates of both gases and liquids is becoming more and more important, driven by numerous economically important applications in for instance semiconductor industry, analytical instrumentation, energy, and micro reaction systems. Accordingly, we hereby announce a special issue addressing advances in design, modeling and simulation, fabrication, and characterization of micromachined mass flow sensors and controllers. Such devices have typically critical feature size on the order of ~1-500 μm and process or design control on a microscale. We invite submission of papers on devices for accurate measurement and control of (extremely) small mass flow rates of both gases and liquids, and corresponding measurement and control principles, for instance the thermal, ultrasonic and Coriolis principles for flow measurement, and the piezo-electric, electromagnetic and electrostatic principles for flow control. Related novel systems concepts, electronic instrumentation and application proposals are acceptable contributions. Moreover, innovative methods in calibration equipment and methodology, micro- and nanomachining, device characterization, etc., are of interest.

I am looking forward to receiving your valuable contributions!

Dr. Joost Lötters
Guest Editor

Keywords

  • flow sensors
  • mass flow sensors
  • flow controllers
  • mass flow controllers
  • thermal flow sensors
  • Coriolis flow sensors
  • ultrasonic flow sensors
  • actuators
  • valves
  • control valves
  • MEMS
  • micromachining
  • electromagnetic actuator
  • piezo-electric actuator
  • electrostatic actuator

Published Papers (14 papers)

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Research

Jump to: Review

Open AccessArticle Simulation and Experimental Characterization of Microscopically Accessible Hydrodynamic Microvortices
Micromachines 2012, 3(2), 529-541; doi:10.3390/mi3020529
Received: 26 April 2012 / Revised: 22 May 2012 / Accepted: 8 June 2012 / Published: 15 June 2012
Cited by 4 | PDF Full-text (1091 KB) | HTML Full-text | XML Full-text
Abstract
Single-cell studies of phenotypic heterogeneity reveal more information about pathogenic processes than conventional bulk-cell analysis methods. By enabling high-resolution structural and functional imaging, a single-cell three-dimensional (3D) imaging system can be used to study basic biological processes and to diagnose diseases such [...] Read more.
Single-cell studies of phenotypic heterogeneity reveal more information about pathogenic processes than conventional bulk-cell analysis methods. By enabling high-resolution structural and functional imaging, a single-cell three-dimensional (3D) imaging system can be used to study basic biological processes and to diagnose diseases such as cancer at an early stage. One mechanism that such systems apply to accomplish 3D imaging is rotation of a single cell about a fixed axis. However, many cell rotation mechanisms require intricate and tedious microfabrication, or fail to provide a suitable environment for living cells. To address these and related challenges, we applied numerical simulation methods to design new microfluidic chambers capable of generating fluidic microvortices to rotate suspended cells. We then compared several microfluidic chip designs experimentally in terms of: (1) their ability to rotate biological cells in a stable and precise manner; and (2) their suitability, from a geometric standpoint, for microscopic cell imaging. We selected a design that incorporates a trapezoidal side chamber connected to a main flow channel because it provided well-controlled circulation and met imaging requirements. Micro particle-image velocimetry (micro-PIV) was used to provide a detailed characterization of flows in the new design. Simulated and experimental results demonstrate that a trapezoidal side chamber represents a viable option for accomplishing controlled single cell rotation. Further, agreement between experimental and simulated results confirms that numerical simulation is an effective method for chamber design. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle A Hybrid Thermopneumatic and Electrostatic Microvalve with Integrated Position Sensing
Micromachines 2012, 3(2), 379-395; doi:10.3390/mi3020379
Received: 20 March 2012 / Revised: 17 April 2012 / Accepted: 24 April 2012 / Published: 27 April 2012
Cited by 3 | PDF Full-text (809 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a low-power hybrid thermopneumatic microvalve with an electrostatic hold and integrated valve plate position sensing. This combination of actuators in a single structure enables a high throw and force actuator with low energy consumption, a combination that is difficult [...] Read more.
This paper presents a low-power hybrid thermopneumatic microvalve with an electrostatic hold and integrated valve plate position sensing. This combination of actuators in a single structure enables a high throw and force actuator with low energy consumption, a combination that is difficult to otherwise achieve. The completed 7.5 mm × 10.3 mm × 1.5 mm valve has an open flow rate of 8 sccm at 600 Pa, a leak rate of 2.2 × 10−3 sccm at 115 kPa, a open-to-closed fluidic conductance ratio of nearly one million, an actuation time of 430 ms at 250 mW, and a required power of 90 mW while closed. It additionally requires no power to open, and has a built-in capacitive position sensor with a sensitivity of 9.8 fF/kPa. The paper additionally presents analytical models of the valve components, design tradeoffs, and guidelines for achieving an optimized device. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Design Considerations for a Micromachined Proportional Control Valve
Micromachines 2012, 3(2), 396-412; doi:10.3390/mi3020396
Received: 6 February 2012 / Revised: 6 April 2012 / Accepted: 24 April 2012 / Published: 27 April 2012
Cited by 5 | PDF Full-text (354 KB) | HTML Full-text | XML Full-text
Abstract
Precise mass flow control is an essential requirement for novel, small-scale fluidic systems. However, a small-volume, low-leakage proportional control valve for minute fluid flows has not yet been designed or manufactured. A survey is therefore made of the primary design considerations of [...] Read more.
Precise mass flow control is an essential requirement for novel, small-scale fluidic systems. However, a small-volume, low-leakage proportional control valve for minute fluid flows has not yet been designed or manufactured. A survey is therefore made of the primary design considerations of a micromachined, proportional control valve. Performance requirements are identified based on various applications. Valve operating principles and actuation schemes presented in the literature are evaluated with respect to functionality and technological feasibility. Proceeding from these analyses, we identify the design concepts and actuation schemes that we think are best suited for the fabrication of the intended microvalve. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Time of Flight Sensor with a Flow Parallel Wire
Micromachines 2012, 3(2), 325-330; doi:10.3390/mi3020325
Received: 5 March 2012 / Revised: 5 April 2012 / Accepted: 18 April 2012 / Published: 26 April 2012
PDF Full-text (306 KB) | HTML Full-text | XML Full-text
Abstract
A time of flight sensor has been equipped with a sensing wire parallel to the flow direction (flow parallel wire, FPW). A heat pulse is generated with a coil in the flow channel. The FPW has a center tap allowing its upstream [...] Read more.
A time of flight sensor has been equipped with a sensing wire parallel to the flow direction (flow parallel wire, FPW). A heat pulse is generated with a coil in the flow channel. The FPW has a center tap allowing its upstream and downstream parts to join in a half bridge. When a heat pulse passes the FPW, a large output peak is generated. The time between heat pulse generation and recording the peak maximum is only marginally affected by the properties of the fluid. With a combination of two FPWs, a measuring range of approximately 0.01–0.5 m/s can be achieved. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Micro-Ramps for Hypersonic Flow Control
Micromachines 2012, 3(2), 364-378; doi:10.3390/mi3020364
Received: 3 March 2012 / Revised: 27 March 2012 / Accepted: 19 April 2012 / Published: 26 April 2012
Cited by 13 | PDF Full-text (5789 KB) | HTML Full-text | XML Full-text
Abstract
Shock/boundary layer interaction (SBLI) is an undesirable phenomenon, occurring in high-speed propulsion systems. The conventional method to manipulate and control SBLI is using a bleed system that involves the removal of a certain amount of mass of the inlet flow to control [...] Read more.
Shock/boundary layer interaction (SBLI) is an undesirable phenomenon, occurring in high-speed propulsion systems. The conventional method to manipulate and control SBLI is using a bleed system that involves the removal of a certain amount of mass of the inlet flow to control boundary layer separation. However, the system requires a larger nacelle to compensate the mass loss, larger nacelles contribute to additional weight and drag and reduce the overall performance. This study investigates a novel type of flow control device called micro-ramps, a part of the micro vortex generators (VGs) family that intends to replace the bleed technique. Micro-ramps produce pairs of counter-rotating streamwise vortices, which help to suppress SBLI and reduce the chances of flow separation. Experiments were done at Mach 5 with two micro-ramp models of different sizes. Schlieren photography, surface flow visualization and infrared thermography were used in this investigation. The results revealed the detailed flow characteristics of the micro-ramp, such as the primary and secondary vortices. This helps us to understand the overall flow physics of micro-ramps in hypersonic flow and their application for SBLI control. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Figures

Open AccessArticle Design Issues for Low Power Integrated Thermal Flow Sensors with Ultra-Wide Dynamic Range and Low Insertion Loss
Micromachines 2012, 3(2), 295-314; doi:10.3390/mi3020295
Received: 27 February 2012 / Revised: 27 March 2012 / Accepted: 5 April 2012 / Published: 10 April 2012
Cited by 5 | PDF Full-text (636 KB) | HTML Full-text | XML Full-text
Abstract
Flow sensors are the key elements in most systems for monitoring and controlling fluid flows. With the introduction of MEMS thermal flow sensors, unprecedented performances, such as ultra wide measurement ranges, low power consumptions and extreme miniaturization, have been achieved, although several [...] Read more.
Flow sensors are the key elements in most systems for monitoring and controlling fluid flows. With the introduction of MEMS thermal flow sensors, unprecedented performances, such as ultra wide measurement ranges, low power consumptions and extreme miniaturization, have been achieved, although several critical issues have still to be solved. In this work, a systematic approach to the design of integrated thermal flow sensors, with specification of resolution, dynamic range, power consumption and pressure insertion loss is proposed. All the critical components of the sensors, namely thermal microstructure, package and read-out interface are examined, showing their impact on the sensor performance and indicating effective optimization strategies. The proposed design procedures are supported by experiments performed using a recently developed test chip,including several different sensing structures and a flexible electronic interface. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Figures

Open AccessArticle A Digitally Controllable Polymer-Based Microfluidic Mixing Module Array
Micromachines 2012, 3(2), 279-294; doi:10.3390/mi3020279
Received: 11 February 2012 / Revised: 15 March 2012 / Accepted: 27 March 2012 / Published: 29 March 2012
Cited by 1 | PDF Full-text (2069 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an integrated digitally controllable microfluidic system for continuous solution supply with a real-time concentration control. This system contains multiple independently operating mixing modules, each integrated with two vortex micropumps, two Tesla valves and a micromixer. The interior surface of [...] Read more.
This paper presents an integrated digitally controllable microfluidic system for continuous solution supply with a real-time concentration control. This system contains multiple independently operating mixing modules, each integrated with two vortex micropumps, two Tesla valves and a micromixer. The interior surface of the system is made of biocompatible materials using a polymer micro-fabrication process and thus its operation can be applied to chemicals and bio-reagents. In each module, pumping of fluid is achieved by the vortex micropump working with the rotation of a micro-impeller. The downstream fluid mixing is based on mechanical vibrations driven by a lead zirconate titanate ceramic diaphragm actuator located below the mixing chamber. We have conducted experiments to prove that the addition of the micro-pillar structures to the mixing chamber further improves the mixing performance. We also developed a computer-controlled automated driver system to control the real-time fluid mixing and concentration regulation with the mixing module array. This research demonstrates the integration of digitally controllable polymer-based microfluidic modules as a fully functional system, which has great potential in the automation of many bio-fluid handling processes in bio-related applications. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Microreactortechnology: Real-Time Flow Measurements in Organic Synthesis
Micromachines 2012, 3(2), 244-254; doi:10.3390/mi3020244
Received: 15 February 2012 / Revised: 15 March 2012 / Accepted: 23 March 2012 / Published: 27 March 2012
Cited by 6 | PDF Full-text (1500 KB) | HTML Full-text | XML Full-text
Abstract
With the commercial availability of integrated microreactor systems, the numbers of chemical processes that are performed nowadays in a continuous flow is growing rapidly. The control over mixing efficiency and homogeneous heating in these reactors allows industrial scale production that was often [...] Read more.
With the commercial availability of integrated microreactor systems, the numbers of chemical processes that are performed nowadays in a continuous flow is growing rapidly. The control over mixing efficiency and homogeneous heating in these reactors allows industrial scale production that was often hampered by the use of large amounts of hazardous chemicals. Accurate actuation and in line measurements of the flows, to have a better control over the chemical reaction, is of added value for increasing reproducibility and a safe production. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Integrated Thermal and Microcoriolis Flow Sensing System with a Dynamic Flow Range of More Than Five Decades
Micromachines 2012, 3(1), 194-203; doi:10.3390/mi3010194
Received: 6 February 2012 / Revised: 23 February 2012 / Accepted: 13 March 2012 / Published: 15 March 2012
Cited by 4 | PDF Full-text (625 KB) | HTML Full-text | XML Full-text
Abstract
We have realized a micromachined single chip flow sensing system with an ultra-wide dynamic flow range of more than five decades, from 100 nL/h up to more than 10 mL/h. The system comprises both a thermal and a micro Coriolis flow sensor [...] Read more.
We have realized a micromachined single chip flow sensing system with an ultra-wide dynamic flow range of more than five decades, from 100 nL/h up to more than 10 mL/h. The system comprises both a thermal and a micro Coriolis flow sensor with partially overlapping flow ranges. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Modeling and Control of Electrowetting Induced Droplet Motion
Micromachines 2012, 3(1), 150-167; doi:10.3390/mi3010150
Received: 1 February 2012 / Revised: 2 March 2012 / Accepted: 12 March 2012 / Published: 14 March 2012
Cited by 5 | PDF Full-text (781 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a general methodology for the dynamic study of electrostatically actuated droplets is presented. A simplified 1D transient model is developed to investigate the transient response of a droplet to an actuation voltage and to study the effect of geometrical [...] Read more.
In this paper, a general methodology for the dynamic study of electrostatically actuated droplets is presented. A simplified 1D transient model is developed to investigate the transient response of a droplet to an actuation voltage and to study the effect of geometrical and fluid-thermal properties and electrical parameters on this behavior. First, the general approach for the dynamic droplet motion model is described. All forces acting on the droplet are introduced and presented in a simplified algebraic expression. For the retentive force, the empirically extracted correlations are used, and for the electrostatic actuation force, results from electrostatic finite element simulations are used. The dynamic model is applied to electrowetting induced droplet motion between parallel plates in the case of a single actuation electrode and for an array of electrodes. Using this methodology, the influence of the switching frequency and actuation voltage is studied. Furthermore, a linearized equivalent damped mass—spring model is presented to approximate the dynamic droplet motion. It is shown that the optimal switching frequency can be estimated by twice the natural frequency of the linearized damped mass—spring system. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
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Open AccessCommunication Displacement Pumping of Liquids Radially Inward on Centrifugal Microfluidic Platforms in Motion
Micromachines 2012, 3(1), 1-9; doi:10.3390/mi3010001
Received: 7 November 2011 / Revised: 12 December 2011 / Accepted: 15 December 2011 / Published: 22 December 2011
Cited by 9 | PDF Full-text (1469 KB) | HTML Full-text | XML Full-text
Abstract
We describe two novel centrifugal microfluidic platform designs that enable passive pumping of liquids radially inward while the platform is in motion. The first design uses an immiscible liquid to displace an aqueous solution back towards the center of the platform, while [...] Read more.
We describe two novel centrifugal microfluidic platform designs that enable passive pumping of liquids radially inward while the platform is in motion. The first design uses an immiscible liquid to displace an aqueous solution back towards the center of the platform, while the second design uses an arbitrary pumping liquid with a volume of air between it and the solution being pumped. Both designs demonstrated the ability to effectively pump 55% to 60% of the solution radially inward at rotational frequencies as low as 400 rpm (6.7 Hz) to 700 rpm (11.7 Hz). The pumping operations reached completion within 120 s and 400 s respectively. These platform designs for passive pumping of liquids do not require moving parts or complex fabrication techniques. They offer great potential for increasing the number of sequential operations that can be performed on centrifugal microfluidic platforms, thereby reducing a fundamental limitation often associated with these platforms. Full article
(This article belongs to the Special Issue Micro Flow Controllers)

Review

Jump to: Research

Open AccessReview Micromachined Thermal Flow Sensors—A Review
Micromachines 2012, 3(3), 550-573; doi:10.3390/mi3030550
Received: 13 June 2012 / Revised: 3 July 2012 / Accepted: 16 July 2012 / Published: 23 July 2012
Cited by 69 | PDF Full-text (683 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Microfabrication has greatly matured and proliferated in use amongst many disciplines. There has been great interest in micromachined flow sensors due to the benefits of miniaturization: low cost, small device footprint, low power consumption, greater sensitivity, integration with on-chip circuitry, etc. This [...] Read more.
Microfabrication has greatly matured and proliferated in use amongst many disciplines. There has been great interest in micromachined flow sensors due to the benefits of miniaturization: low cost, small device footprint, low power consumption, greater sensitivity, integration with on-chip circuitry, etc. This paper reviews the theory of thermal flow sensing and the different configurations and operation modes available. Material properties relevant to micromachined thermal flow sensing and selection criteria are also presented. Finally, recent applications of micromachined thermal flow sensors are presented. Detailed tables of the reviewed devices are included. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Figures

Open AccessReview Hydrodynamic Flow Confinement Technology in Microfluidic Perfusion Devices
Micromachines 2012, 3(2), 442-461; doi:10.3390/mi3020442
Received: 24 March 2012 / Revised: 18 April 2012 / Accepted: 2 May 2012 / Published: 10 May 2012
Cited by 5 | PDF Full-text (1752 KB) | HTML Full-text | XML Full-text
Abstract
Hydrodynamically confined flow device technology is a young research area with high practical application potential in surface processing, assay development, and in various areas of single cell research. Several variants have been developed, and most recently, theoretical and conceptual studies, as well [...] Read more.
Hydrodynamically confined flow device technology is a young research area with high practical application potential in surface processing, assay development, and in various areas of single cell research. Several variants have been developed, and most recently, theoretical and conceptual studies, as well as fully developed automated systems, were presented. In this article we review concepts, fabrication strategies, and application areas of hydrodynamically confined flow (HCF) devices. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessReview Micromachined Flow Sensors in Biomedical Applications
Micromachines 2012, 3(2), 225-243; doi:10.3390/mi3020225
Received: 23 February 2012 / Revised: 6 March 2012 / Accepted: 21 March 2012 / Published: 26 March 2012
Cited by 21 | PDF Full-text (955 KB) | HTML Full-text | XML Full-text
Abstract
Application fields of micromachined devices are growing very rapidly due to the continuous improvement of three dimensional technologies of micro-fabrication. In particular, applications of micromachined sensors to monitor gas and liquid flows hold immense potential because of their valuable characteristics (e.g., low [...] Read more.
Application fields of micromachined devices are growing very rapidly due to the continuous improvement of three dimensional technologies of micro-fabrication. In particular, applications of micromachined sensors to monitor gas and liquid flows hold immense potential because of their valuable characteristics (e.g., low energy consumption, relatively good accuracy, the ability to measure very small flow, and small size). Moreover, the feedback provided by integrating microflow sensors to micro mass flow controllers is essential to deliver accurately set target small flows. This paper is a review of some application areas in the biomedical field of micromachined flow sensors, such as blood flow, respiratory monitoring, and drug delivery among others. Particular attention is dedicated to the description of the measurement principles utilized in early and current research. Finally, some observations about characteristics and issues of these devices are also reported. Full article
(This article belongs to the Special Issue Micro Flow Controllers)

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